diff --git a/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td b/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td
index 0c04457..c88c097 100644
--- a/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td
+++ b/include/p4mlir/Dialect/P4HIR/P4HIR_Ops.td
@@ -1002,13 +1002,16 @@ def InstantiateOp : P4HIR_Op<"instantiate",
    DeclareOpInterfaceMethods<OpAsmOpInterface, ["getAsmResultNames"]>]> {
   let summary = "constructor call operation";
   let description = [{
-    Instantiate P4 object: extern, parser, control or package/
+    Instantiate P4 object: extern, parser, control or package.
 
     Example:
 
     ```mlir
-    // Direct call of function
-    %2 = p4hir.call @my_add(%0, %1) : (!p4hir.bit<8>, !p4hir.bit<8>) -> !p4hir.bit<8>
+    // Instantiate a subparser
+    %sp = p4hir.instantiate @subparser() as "sp" : () -> !p4hir.parser<"subparser", (!empty)>
+    // Instantiate a subparser with ctor parameters
+    %false = p4hir.const #false
+    %sp2 = p4hir.instantiate @subparser2(%false) as "sp2" : (!p4hir.bool) -> !p4hir.parser<"subparser2", (!empty)>
     ...
     ```
   }];
@@ -1054,6 +1057,51 @@ def InstantiateOp : P4HIR_Op<"instantiate",
   }];
 }
 
+def ApplyOp : P4HIR_Op<"apply",
+  [NoRegionArguments, CallOpInterface,
+   //DeclareOpInterfaceMethods<OpAsmOpInterface, ["getAsmResultNames"]>
+    TypesMatchWith<
+       "the apply type of the object matches the types of operands",
+       "callee", "arg_operands", "cast<P4HIR::ParserType>($_self).getInputs()">,
+   ]> {
+  let summary = "apply operation";
+  let description = [{
+    Applies P4 parser, table or control
+
+    Example:
+
+    ```mlir
+    // Application of a subparser
+    %sp = p4hir.instantiate @subparser() as "sp" : () -> !p4hir.parser<"subparser", ()>
+    p4hir.apply %sp() : !p4hir.parser<"subparser", ()>
+    ...
+    ```
+  }];
+
+  // TODO: Refine result types, refine parameter type (must be constants!)
+  let results = (outs);
+  let arguments = (ins P4ObjectType:$callee, Variadic<AnyType>:$arg_operands);
+
+  // TODO: Add verifier
+  let hasVerifier = 0;
+
+  let extraClassDeclaration = [{
+    /// Return the callee of this operation.
+    mlir::CallInterfaceCallable getCallableForCallee() {
+      return getCallee();
+    }
+
+    /// Set the callee for this operation.
+    void setCalleeFromCallable(mlir::CallInterfaceCallable callee) {
+      getCalleeMutable().assign(callee.get<mlir::Value>());
+    }
+  }];
+
+  let assemblyFormat = [{
+    $callee `(` $arg_operands `)` attr-dict `:` type($callee)
+  }];
+}
+
 
 include "p4mlir/Dialect/P4HIR/P4HIR_ParserOps.td"
 
diff --git a/test/Translate/Parser/subparser.p4 b/test/Translate/Parser/subparser.p4
index cff7c90..ff6e58e 100644
--- a/test/Translate/Parser/subparser.p4
+++ b/test/Translate/Parser/subparser.p4
@@ -14,23 +14,39 @@ parser subparser2(in empty e)(bool ctorArg) {
     }
 }
 
-// CHECK-LABEL: p4hir.parser @p
-// CHECK: p4hir.instantiate @subparser() as "sp" : () -> !p4hir.parser<"subparser", (!empty)>
-// CHECK: %[[false:.*]] = p4hir.const #false
-// CHECK: p4hir.instantiate @subparser2(%[[false]]) as "sp2" : (!p4hir.bool) -> !p4hir.parser<"subparser2", (!empty)>
+parser subparser3(inout int<10> s, out bool matched)() {
+    state start {
+        transition accept;
+    }
+}
 
+// CHECK-LABEL: p4hir.parser @p(%arg0: !empty, %arg1: !i10i)()
 parser p(in empty e, in int<10> sinit) {
     int<10> s = sinit;
     subparser() sp;
     subparser2(false) sp2;
+    subparser3() sp3;
+// CHECK: %[[sp:.*]] = p4hir.instantiate @subparser() as "sp" : () -> !p4hir.parser<"subparser", (!empty)>
+// CHECK: %[[false:.*]] = p4hir.const #false
+// CHECK: %[[sp2:.*]] = p4hir.instantiate @subparser2(%[[false]]) as "sp2" : (!p4hir.bool) -> !p4hir.parser<"subparser2", (!empty)>
+// CHECK: %[[sp3:.*]] = p4hir.instantiate @subparser3() as "sp3" : () -> !p4hir.parser<"subparser3", (!p4hir.ref<!i10i>, !p4hir.ref<!p4hir.bool>)>
 
     state start {
         s = 1;
+        sp.apply(e);
+// CHECK: p4hir.apply %[[sp]](%arg0) : !p4hir.parser<"subparser", (!empty)>
         transition next;
     }
-    
+
     state next {
         s = 2;
+        sp2.apply(e);
+// CHECK: p4hir.apply %[[sp2]](%arg0) : !p4hir.parser<"subparser2", (!empty)>
+// CHECK: p4hir.scope
+// CHECK: p4hir.apply %[[sp3]](%s_inout_arg, %matched_out_arg) : !p4hir.parser<"subparser3", (!p4hir.ref<!i10i>, !p4hir.ref<!p4hir.bool>)>
+        bool matched = false;
+        sp3.apply(s, matched);
+
         transition accept;
     }
 
diff --git a/tools/p4mlir-translate/translate.cpp b/tools/p4mlir-translate/translate.cpp
index f164412..8fd8b5f 100644
--- a/tools/p4mlir-translate/translate.cpp
+++ b/tools/p4mlir-translate/translate.cpp
@@ -545,8 +545,10 @@ bool P4TypeConverter::preorder(const P4::IR::Type_Parser *type) {
     ConversionTracer trace("TypeConverting ", type);
 
     llvm::SmallVector<mlir::Type, 4> argTypes;
-    for (const auto *p : type->getApplyParameters()->parameters)
-        argTypes.emplace_back(convert(p->type));
+    for (const auto *p : type->getApplyParameters()->parameters) {
+        mlir::Type type = convert(p->type);
+        argTypes.push_back(p->hasOut() ? P4HIR::ReferenceType::get(type) : type);
+    }
 
     auto mlirType = P4HIR::ParserType::get(converter.context(), type->name.string_view(), argTypes);
     return setType(type, mlirType);
@@ -1340,6 +1342,14 @@ bool P4HIRConverter::preorder(const P4::IR::MethodCallExpression *mce) {
             BUG_CHECK(fSym, "expected reference function to be converted: %1%", fCall->method);
 
             callResult = b.create<P4HIR::CallOp>(loc, fSym, callResultType, operands).getResult();
+        } else if (const auto *aCall = instance->to<P4::ApplyMethod>()) {
+            LOG4("resolved as apply");
+            // Apply of something instantiated
+            if (auto *decl = aCall->object->to<P4::IR::Declaration_Instance>()) {
+                auto val = getValue(decl);
+                b.create<P4HIR::ApplyOp>(loc, val, operands);
+            } else
+                BUG("Unsuported apply: %1%", aCall->object);
         } else {
             BUG("unsupported call type: %1%", mce);
         }
@@ -1699,9 +1709,10 @@ bool P4HIRConverter::preorder(const P4::IR::Declaration_Instance *decl) {
         auto parserSym = p4Symbols.lookup(parser);
         BUG_CHECK(parserSym, "expected reference parser to be converted: %1%", dbp(parser));
 
-        builder.create<P4HIR::InstantiateOp>(getLoc(builder, decl), resultType,
-                                             parserSym.getRootReference(), operands,
-                                             builder.getStringAttr(decl->name.string_view()));
+        auto instance = builder.create<P4HIR::InstantiateOp>(
+            getLoc(builder, decl), resultType, parserSym.getRootReference(), operands,
+            builder.getStringAttr(decl->name.string_view()));
+        setValue(decl, instance.getResult());
     } else {
         BUG("unsupported instance type: %1%", decl);
     }