Toast rolled oats in a heated pan without oil. The finished oats should be a darker color, and smell toasted.
Heat balsamic vinegar in a small saucepan over medium heat. Bring to a gentle boil, then reduce heat to medium-low heat and let simmer, stirring occasionally, until the vinegar thickens and is reduced to desired thickness. The reduction should be at least half of the original amount.
Heat oil in a medium skillet over medium-high. Add onion and cook, stirring occasionally, until tender, 3 to 4 minutes. Stir in oats; cook 1 minute. Add water and bring to a boil. Reduce heat to medium, and simmer, stirring often, until oats are tender, about 8 minutes. Remove from heat.
Stir ¾ cup cheese, ¾ teaspoon salt, and ¼ teaspoon pepper into oats mixture. Spoon ½ cup of oats mixture into each of 4 serving bowls; top each with ½ cup spinach and 1 poached egg. Sprinkle evenly with remaining 1 teaspoon each salt and pepper, and top evenly with remaining ¼ cup cheese. Sprinkle evenly with fresh herbs and balsamic reduction.
