In the large skillet, heat the olive oil and cook the onions over medium-high heat for about 2 minutes. Add the garlic and the remaining vegetables and cook for about 2 minutes, just until the vegetables start to glisten. Add the wine and lemon juice and stir. Pat the mahi-mahi fillets dry with paper towels and lay on top of the vegetables. Salt and pepper the top side of the fillets to taste. Cover and cook 4 to 5 minutes. Turn the fillets over and salt and pepper side to taste. Cook another 4 to 5 minutes or until the fish flakes easily. Squeeze some more lemon juice on top and serve immediately.
