In large pot of boiling water, cook pasta until tender, but firm; drain.
As pasta is cooking, heat 1 teaspoons oil in a skillet. Add chicken and sauté 3-4 minutes or until almost cooked. Add red and orange peppers and spinach; sauté for another 3-4 minutes.
Stir in lemon juice. Transfer mixture to a bowl and set aside.
In the same pot used for pasta, heat remaining oil (2 tsp.) over medium heat; blend in flour. Add garlic, milk and pepper. Cook, whisking constantly until mixture comes to a boil. Reduce heat and simmer for 2-3 minutes.
Remove from heat. Add cheese and stir until blended.
Add pasta, chicken and vegetables to sauce; stir until combined.