Cook tortellini in boiling water according to package directions. Add the carrots during the last 5 minutes of cooking, the zucchini during the last 3 minutes, and the sugar snap peas during the last 1 minute of cooking. Drain and set aside.
Meanwhile, shake together chicken broth, oregano, flour, salt, pepper, and milk in a screw-top jar until smooth.
Heat butter in a separate pot. Add garlic, and cook just 60 seconds until fragrant. Add broth mixture, and cook and stir until thickened and bubbly. Add cream cheese. Cook and stir until cream cheese is smooth. Remove from heat. Stir in lemon juice.
Add pasta mixture, chicken, tomatoes, and sweet pepper. Toss to coat. Turn into an ungreased 13x9x2-inch baking dish or shallow 3-quart casserole.
Bake, covered, in a 350 degrees F oven for 20 to 25 minutes or until heated through. Stir mixture and sprinkle with Parmesan cheese.